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[PATCH 16/25] quota: Verify flags passed to Q_SETINFO

To: linux-fsdevel@xxxxxxxxxxxxxxx
Subject: [PATCH 16/25] quota: Verify flags passed to Q_SETINFO
From: Jan Kara <jack@xxxxxxx>
Date: Thu, 18 Dec 2014 16:37:30 +0100
Cc: xfs@xxxxxxxxxxx, cluster-devel@xxxxxxxxxx, ocfs2-devel@xxxxxxxxxxxxxx, Jan Kara <jack@xxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1418917059-23870-1-git-send-email-jack@xxxxxxx>
References: <1418917059-23870-1-git-send-email-jack@xxxxxxx>
Currently flags passed via Q_SETINFO were just stored. This makes it
hard to add new flags since in theory userspace could be just setting /
clearing random flags. Since currently there is only one userspace
settable flag and that is somewhat obscure flags only for ancient v1
quota format, I'm reasonably sure noone operates these flags and
hopefully we are fine just adding the check that passed flags are sane.
If we indeed find some userspace program that gets broken by the strict
check, we can always remove it again.

Signed-off-by: Jan Kara <jack@xxxxxxx>
 fs/quota/dquot.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index a6b5795a4181..02d571cb010a 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -2649,6 +2649,14 @@ int dquot_set_dqinfo(struct super_block *sb, int type, 
struct if_dqinfo *ii)
                goto out;
        mi = sb_dqopt(sb)->info + type;
+       if (ii->dqi_valid & IIF_FLAGS) {
+               if (ii->dqi_flags & ~DQF_SETINFO_MASK ||
+                   (ii->dqi_flags & DQF_ROOT_SQUASH &&
+                    mi->dqi_format->qf_fmt_id != QFMT_VFS_OLD)) {
+                       err = -EINVAL;
+                       goto out;
+               }
+       }
        if (ii->dqi_valid & IIF_BGRACE)
                mi->dqi_bgrace = ii->dqi_bgrace;

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